Piezo-electric apparatus



Febl9, 1932- A. B. TRIPP PIEZO ELECTRIC APf'ARATUS Filed May 1. 1928 Wby Mi His Attorney.

Patented Feb. 9, 1932 UNITED STATES PATENT OFFICE AUGUSTUS B. TRIPP, OFCLIFTONDALE, MASSACHUSETTS, ASSIGNOR T GENERAL ELEC- TRIO COMPANY, ACORPORATION OF NENV YORK PIEZO-ELECTRIC APPARATUS Application filed May1,

My invention relates to piezo-electric apparatus, and has for itsprincipal object the provision of an improved piezo-electric cell whichis so constructed as to permit ready assembly and accurate adjustment ofits various parts.

It is wellknown that a piezo-electric element, such as a crystal ofquartz or the like, will oscillate at a frequency dependent on itsmechanical dimensions when it is subjected to an electrostatic field andthat this characteristic of the piezo-electric element may be utilizedto predetermine very accurately the frequency at which current issupplied from a source to an output circuit. It is de sirable that theelectrodes through which the electro-static field is applied to theactive surfaces of the element be capable of accurate adjustment withrespect to one another. In making this adjustment, the element may besubjected to a compressive force applied through the electrodes or mayrest upon one of the electrodes and be slightly spaced from the other.The latter arrangement has the advantage that oscillation of the elementis readily initiated but has the disadvantage that the output is not soconstant as it is when the element is subjected to slight pressure. Inaccordance with my invention, variation in the output is avoided by theprovision of an improved cell including a resilient mechanical couplingwhich permits very accurate adjustment in the pressure applied to theactive surfaces of the piezo-electric element.

My invention will be better understood from the following descriptionwhen considered in connection with the accompanying drawing and itsscope will be pointed out in the appended claims.

The drawing illustrates a piezo-electric ap paratus constructed inaccordance with my invention.

This apparatus includes a piezoelectric element 1 which is interposedbetween an adjustable electrode 2 and a floating electrode 8. Thiselement is surrounded at its outer edges by an insulation collar 4, andis protected from variations in temperature by an insulation cover 5mounted on an insula- 18%8. Setialflo. 274,3".

tion base 6. Potential is applied to the adjustable electrode 2 througha terminal 8 and a threaded support 9 and to the floating electrode 3through a terminal 7, a threaded pedestal 10, an adjusting member '11threaded into the pedestal 10 and a bolt 12 or a spiral spring 13 whichsurrounds the bolt 12 and is interposed between the adjusting member 11and the electrode 3. 7

With this construction, the adjustable mechanical coupling between theelectrodes 2 and 3 includes the member 9, the base 6, the pcdestal lO,the adjusting member 11, the bolt 12 and the spring 13. A It should benoted that the floating electrode 3, the spring 13, the bolt 1:? and thethreaded plug or adjusting member 11 are arranged to form a unitassembly which may be adjusted readily to apply any desired pressure tothe active surfaces of the element 1. The proper adjust- 5 meat of theelectrode 2 is preferably made by first screwing it down until thefloating electrode 3 is clamped against the top of the pedestal 10 bypressure exerted through the element 1 and then unscrewing the electrodei 2 slightly so as to free the floating electrode 3 and leave it pressedagainst the element 1 by a pressure dependent on the adjustment of theunit assembly formed by the members 3, 11, 12 and 13. The maintenance ofthe electrodes in contact with the active surfaces of the piezo-electricelement has the advantage that change in output due to temperaturevariations is largely avoided. This advantage is most marked in the caseof very thin elements.

The floating electrode 3 and the element 1 are prevented from lateraldisplacement by the insulation barrier 4 which closely fits the upperperiphery of the pedestal 10 and keeps the element 1 between theelectrodes 2 and 3. It has been found that a piezoelectric cell of thisconstruction can be roughly treated without damage and can besatisfactorily used in any desired position.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. In a piezo-electric apparatus, a unit assembly including a floatingelectrode, an adjusting member, a member fixed to said hand this 28thfloating electrode and extending through said adjusting member, and aspiral spring interposed between said adjusting member and said floatingelectrode.

2. In a piezo-electric apparatus, a unit assembly includi'ng a floatingelectrode, an adjusting member, a pin fixed to said electrode andextending through said adjusting member, and a spiral spring surroundingsaid pin and extending between said floating electrode and saidadjusting member.

3. In a piezo electric apparatus, the combination of a unit assemblyincluding a floating electrode, an adjustable electrode spaced from saidfloating electrode for forming a crystal chamber, a spring arranged tosupport said floating electrode and means comprising a pair of threadedmembers for ad- 7 justing the position of said spring.

4:; In a piezo electric apparatus, the combination of an adjustableelectrode, a floating electrode spaced from said adjustable electrodefor forming a crystal chamber, an adjusting member, and a spiral springinterposed between said floatlng electrode and said adjusting member. p

In witness whereof, I have hereunto set my day of April, 1928. AUGUSTUSB. TRIPP.

